Over recent decades most of the marine shipping industry has converted to containerized cargo, wherein products are loaded into large containers (referred to from time-to-time herein as sea containers or shipping containers) of a size approaching that of a conventional truck cargo van, with the containers in turn being loaded onto ships. This allows for economical loading of the individual containers at locations and at rates dictated by convenience, uninfluenced by the significant cost of lay time for a seagoing vessel. Likewise, when the containers are unloaded from the vessel they may be transported by truck or train (i.e., intermodally) to their destinations where the unloading of the individual containers will take place.
The containers are built to standardized patterns, typically having a rectangular framework that supports top, bottom, side and front walls, with doors being pivotally mounted on vertical posts at the rear corners of the container. For example, 13.6 m swapbody containers currently exist, built to ISO (International Organization for Standardization) specifications. These containers normally have corrugated steel sides strengthened by vertical posts at locations 12.2 m (40 feet) apart along the sides. At the top and bottom of each post is a lift point formed by a standard ISO fitting (commonly referred to as a corner casting) that allows the container to be top-lifted by a conventional spreader using twistlock connectors. Also, the construction allows standard laden containers to be stacked atop one another.
The adoption of standardized shipping containers has provided significant benefits with respect to the transportation of non-bulk cargo, nevertheless certain inefficiencies remain, notably in connection with the loading and unloading of the contents of the containers at the end points of their journeys. For example, multiple containers may become backed up at warehouses or other destinations due to limited facilities, each container waiting for its turn at a loading dock or bay. Moreover, some destinations lack loading docks or bays at all, such that the cargo must be painstakingly unloaded—often by hand—from the deck of the container to the ground and vice versa, resulting in significant costs and delays. Some destination therefore become bottlenecks in terms of cargo movement and dead time for the containers themselves, especially smaller warehouses or other locations having limited or loading/unloading facilities. Road-going motor-truck vans may include lift gates mounted at the rear to aid in loading and unloading, however ISO shipping containers lack the truck chassis to which lift gates are mounted, and furthermore including lift gates would be prohibitively expensive and would also interfere with the containers being stacked on ships or rail cars.